How to Check Database Size in MySQL Quickly

To check the size of a MySQL database, use the information_schema database and query the TABLES table to sum data_length and index_length. This shows the total size in bytes for the specified database.

Syntax

Use this SQL query to find the size of a database in MySQL:

• TABLE_SCHEMA: The name of your database.
• data_length: Size of the data stored.
• index_length: Size of the indexes.
• The sum of data_length and index_length gives the total size in bytes.

sql

SELECT
  table_schema AS 'Database',
  ROUND(SUM(data_length + index_length) / 1024 / 1024, 2) AS 'Size (MB)'
FROM information_schema.TABLES
WHERE table_schema = 'your_database_name'
GROUP BY table_schema;

Example

This example shows how to check the size of a database named shop. It sums the data and index sizes and converts the result to megabytes (MB) rounded to two decimals.

sql

SELECT
  table_schema AS 'Database',
  ROUND(SUM(data_length + index_length) / 1024 / 1024, 2) AS 'Size (MB)'
FROM information_schema.TABLES
WHERE table_schema = 'shop'
GROUP BY table_schema;

Output

Database | Size (MB)
shop     | 12.34

Common Pitfalls

Common mistakes when checking database size include:

• Forgetting to replace 'your_database_name' with the actual database name.
• Not summing both data_length and index_length, which underestimates size.
• Confusing table size with database size by querying individual tables only.

sql

/* Wrong: Only data_length, missing index size */
SELECT
  table_schema AS 'Database',
  ROUND(SUM(data_length) / 1024 / 1024, 2) AS 'Size (MB)'
FROM information_schema.TABLES
WHERE table_schema = 'shop'
GROUP BY table_schema;

/* Correct: Sum data_length and index_length */
SELECT
  table_schema AS 'Database',
  ROUND(SUM(data_length + index_length) / 1024 / 1024, 2) AS 'Size (MB)'
FROM information_schema.TABLES
WHERE table_schema = 'shop'
GROUP BY table_schema;

Quick Reference

Term	Description
TABLE_SCHEMA	Name of the database
data_length	Size of table data in bytes
index_length	Size of table indexes in bytes
SUM(data_length + index_length)	Total size of database in bytes
ROUND(... / 1024 / 1024, 2)	Convert bytes to megabytes with 2 decimals

Key Takeaways

Use information_schema.TABLES to get database size in MySQL.

Sum data_length and index_length for accurate size measurement.

Convert bytes to megabytes by dividing by 1024 twice.

Always specify the correct database name in the query.

Check both data and index sizes to avoid underestimating.